From: Chad Perrin <perrin@...>
Date: 2008-11-16T02:20:41+09:00
Subject: IO#lineno= doesn't work the way I expected

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I'm working on something that operates on each line of a file
individually.  So far, the relevant part looks something like this:

    in_fh =3D File.open(infile, 'r')
    out_fh =3D File.open(outfile, 'w')

    in_fh.each_line do |l|
      out_fh << l
    end

Obviously not the actual working code (since it doesn't do anything other
than copy the file), but it's the simplified version I'm using to test a
feature, anyway.

This works exactly as expected.  I get a duplicate of the input file,
with the name assigned to the outfile variable.

So . . . I want to be able to skip a number of lines at the beginning of
the input file.  It seemed like IO#lineno=3D would be the obvious solution:

    in_fh =3D File.open(infile, 'r')
    out_fh =3D File.open(outfile, 'w')

    in_fh.lineno =3D 1

    in_fh.each_line do |l|
      out_fh << l
    end

Unfortunately, that doesn't give me what I expected at all.  In fact,
what I end up with is an empty file.  Am I misunderstanding what
IO#lineno=3D does?  Is there something about the way IO#each_line works
that is interacting badly with an incremented line number?  What do I
need to do differently to make this work?

--=20
Chad Perrin [ content licensed PDL: http://pdl.apotheon.org ]
Quoth Dennis Miller: "Bill Gates is a monocle and a Persian Cat away
from being the villain in a James Bond movie."

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